Variable-pitch propeller



Jan. 5, 1932. J. P. R0551 1,839,895

VARIABLE PI TCH PROPELLER Filed Jan. 21. 1929 2 Sheets-Sheet 1 ENTOR. aw,

ATTORNEY Jan. 5, 1932. J. P. ROSSI VARIABLE PITCH PROPELLER Filed Jan. 21, 1929 2 Sheets-Sheet 2 J 7 INVENTOR.

Patented Jane 5, 1332 are? OFFICE JOSEPH P. ROSSI, OF EL GERRITO, CALIFORNIA, ASSIGNOR 'OF ONE-TENTH TO CLARENCE BRENSEL, ONE-TENTH TO LOUIS E. NAVELLIER, 01\TETENTH TO EARLW. JOHNSON, ONE-TEN TH TO ANGELO FARA, ONE-TENTH TO VICTT'ORIO MERLOTTI, AND OF ONE- FOURTH TO L. W. EVANS VARIABLE-PITCH .E'ROIPELLER The invention relates to variable pitch propellers and particularly to a means for controlling the pitch of such propellers.

A general object of the invention is to provide a simplified and generally improved propeller which is arranged to have the pitch thereof varied between forward and reverse positions while the propeller is operatively rotating in a given direction.

Another object of the invention is to provide a structure permitting an individual and independent replacement of the blades thereof.

A further object of the invention is to pro- L1 vide in a propeller of they class describeda positive stop for limiting the pitch which the blades are permitted to assume.

Yet another object of the invention is to provide means for adjustably varying the maximum pitch permitted the blades.

Astill further object is to provide an improved and simplified mechanism for controlling the pitch of the blades.

Still another object of the invention is to provide for, and assure, a proper lubrication for the parts of the control mechanism.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth, in the following description of a preferred form of the invention which is illustrated in the accompanying drawings, in which:

Figure 1 is a plan View showing an installation of the propeller and control mechanism in association with a drive shaft of an engine, the propeller blades being inoperatively disposed in a position of zero pitch.

Figure 2 is a sectional plan view .of the showing of Figure 1 taken generally at the plane of the drive shaft axis.

Figure 3 is a view taken at the broken line 3-3 in Figure 2 and rotated through 90 degrees.

Figure 4 is a view taken'on the broken line 4=4 in Figure 2.

Figure 5 is a the installation, showing in full lines the relations of the adjustable parts when the propeller blades are set for an extreme positive or forward pitch thereof and in dash lines fragmentary side view of;

the corresponding relations for a negative or reverse pitch of the blades.

Figure 6 is a view taken generally on the line 66 in Figure 4.

Figure 7 is a face view of an indicator and hand wheel forming parts of the pitch controlling mechanism and as disclosed in Figures 1 and 4.

As herewith particularly shown, the invention is incorporated in and with the structure of a two-bladed aeroplane propeller 8 mounted on a shaft 9 of an engine 11, the latter being indicated only in outline. The propeller is seen to comprise a generally cylindrical one-piece hub 12 having removably mounted thereon blades 13 of suitable design. For mounting the blades on the hub, the blade shanks 14 are journalled in radial bores 15 of the hub and extend into hub cavities 16 at the inner ends of said bores. Plane annular faces 17 are provided at the outer" ends of the bores 15 against which shoulders 18 provided on the blade shanks are arranged to abut for limiting the inward insertion of the blade shanks in the hub. A plane face is also provided for the cavity sides 19 which lie at the inner end of each bore 15, said faces being perpendicular to the axes of the associated bores and providing bearings for the outer ends of annular flange members 21 which are provided on the inner shank ends.

If the hub were made as a pair of sections axially separable at the blade shank axes, the members 21 might be permanently fixed to, or-form' an integral part of, the inner shank ends. But such a method of assembly involves the provision and use of special meansfor securing the sections together as well as the necessity for an exact fitting of such sections at their abutting surfaces. Furthermore, unless the hub be further complicated by a division of the sections, the replacement of one blade would involve the reassembly of theentire propeller structure. In accordance with the present invention, the foregoing and other diiiiculties are avoided by providing for a detachable mounting of each member 21 on its blade shank after said shank is inserted in a bore 15 of the one-piece hub 12.

Any suitable means may be provided for securing a member 21 to its shank, a preferred construction being illustrated in which the shank portion protruding into the cavit 16 is arranged to threadedly receive the ange member 21. Preferably, and as shown, the threaded. shank portion is reduced to provide a shoulder 22 at its outer end against which the member 21 is arranged to abut in generally locked relation when mounted on the shank. To further secure the member 21 to the shank, a pin 23 may be utilized, said pin threadedly engaging the member 21 and extending diametrically through the member and shank. Preferably, the shank ends are square-threaded and are appropriately provided with right and left-hand threads whereby the tightening of the members 21 on the shanks will be urged when the blades are set for traction. The spacing of the outer shank shoulder 18 and the bearing end of the -member 21 is, of course, such as will allow a rotation of the blade shank in the hub bore 15. With the specific blade mounting structure shown and described, the mounting of a blade is simply effected by holding a member 21 in place against the rotation thereof, screwing a shank end thereinto, and installing the pin 23; re-

-moval of a blade is, of course, effected by reversing the last two operations and the order of their performance. In this manner,

' an independent and simple mounting is provided'for each blade.

Besides their use as a means to hold the blades in the hub, the members 21 are also utilized in disposing and holding the blades in positions of different pitch thereof. Ac-

cordingly, the members 21 are provided on their peripheries with gear teeth 24 and racks 25 are provided for operative engagement with said teeth for rotating the blades in their bearings in the hub. Since the maximum desired adjustment of the blades from the neutral, or inoperative, position shown in Figures-1 to 4, would seldom exceed 45 degrees of angle, the gear teeth 24 are only utilized through an arc of about 90 degrees, and so need extend only partly around the members 21, as shown. The teeth 24 are preferably provided on integral portions 26 of the members 21, and said members are thus seen to constitute a segmental gear or pinion and will, on occasion, be hereinafter so referred to. The arcuate toothed portions 26 of the members 21, it is noted, extend outwardly of their inner, or hub, portions 27 and terminate in radial faces 28, said faces preferably being spherically cupped, as shown, and being utilized in a manner to be hereinafter brought out.

Each hub cavity 16, it will now be noted, extends axially of and completely through the hub 12, and is defined between the side 19 previously mentioned as providing a bearerably, and as shown, the cavities .16 are of rectangular and uniform section transversely of the hub axis; in this manner, thesecavities may be formed and finished to provide the bearing face of the side 19 and the guideway for the rack with particular readiness,

it being noted that the hub 12 is preferably a cast member of aluminum composition. The racks are seen to be movable axially of the hub, and are also of rectangular section.

Mounted on the shaft 9, and splined thereto for rotation therewith and for axial movement therealong, is a sleeve member 32. For purposes of assembly, the member 32 is formed with axially separable outer and inner sections 33 and 34 fixed together as by screws 35. The sleeve section 33 is in the form of an annular disc and the inner ends of the racks 25 are fixed thereto as by screws 36. The sleeve section 34 is provided intermediate its ends with an extending annular flange portion 37, said flange being engageable by a collar 38 for axially shifting the member 32 along the shaft 9 for actuating the rack to con'trollably and correspondingly vary the pitch angles of the various propeller blades.

As shown, the collar 38 is formed to provide an inwardly opening annular groove 39 for enclosing the sleeve flange 37, and comprises axially separable sections 41 and 42 fixed together by screws 43 to permit the assembly of the collar about the flange. Antifriction means are preferably provided between the axially opposed flange and collar faces 44 and 45 respectively, and said faces are accordingly here shown provided with opposed races 46 and 47 for the reception of ball bearings 48. In this manner the collar 38 is arranged to be maintained in engaged and centered relation to the sleeve 32, it being clear that the flange 37 rotates within the collar groove 39, the collar being held against rotation. It is to be particularly noted that the specific shift collar connection shown and described is such as provides for a proper lubrication of the ball bearings 48 in their races 46 and 47, since a lubricant in the groove 39 will, through the rotation of the flange 37 therein, tend to remain in the outermost, or bottom, portion of the groove and so conserve the lubricant for repeated use. As shown, a grease cup 49-is mounted at the top of the collar, and a passage is provided from said cup to the collar groove whereby a suitto the rear thereof; as shown, the rods 51 are secured to and extend from diametrically opposite ears 52 provided on the shift collar 88. and extend rearwardly beyond the engine to a spider 53 to the arms of which they are attached. The spider 53 is provided centrally thereof and generally axially of the shaft axis with a threaded opening for the reception of a jack screw 54 mounted for rotation in a fixed supporting member 55. One end of the screw 54 is swivelled in the member 55, while the other end thereof is provided with a. handwheel 56 disposed within easy reach of an operator, as at the instrument board 57 of the. aeroplane.

If desired, detent means may be provided for retaining the hand-wheel in set position, a spring pressed detent 58 being here shown mounted on said instrument board for engagement with sockets provided in the opposed face of the wheel, the hold of said detents being overcome when the operator turns the wheel. A pitch indicator 59 is also provided, said indicator being also mounted on the instrument board 57 and being operated from the spider as by a lever arm 60 extending therefrom, it being noted that the specific structure of said indicator forms no part of the present invention. Connection of the indicator is made to the spider rather than to the wheel because of the fact that the wheel makes a number of revolutions during the range of possible pitch adjustments.

It will now be clear that the device of my invention is arranged to permit a shifting of blade pitch between a desired maximum pulling or positive pitch and a suitable reverse or negative pitch, there being an intermediate position of zero pitch which is that shown in Figures 1 to 4 inclusive. In the use of aeroplane propellers, a pitch value which is best for one set of conditions (such as of altitude, wind direction, and wind velocity) would be very ineflicient under other conditions, and the present device is seen to permit the adjustment required to meet conditions under which the propeller is actually used and while those conditions obtain. A further ideal condition of operation of an aeroplane is that the engine speed be substantially constant and relatively high at all times, and with the present propeller such may be effected through lowering the draft pitch as the ve hicle speed is decreased, thus permitting a maintenance of the engine speed. Reversal of the propeller blades to a negative pitch would be utilized for quickly slowing the aeroplane speed for landing or other purposes. A pitch control device permitting adjustment during the operation of a propeller is thus seen to have a wide and useful application for propellers for use both with air and water vehicles, and the present device is seen to provide a particularly simple and positive means for effecting the pitch control of such propellers during the operation thereof.

By reference to Figures 2 and 3, it is seen that the racks 25 so engage the segmental gear members 21 that they are under tension when the pitch of the propeller blades is positive. This tension on the racks increases with the pitch and is greatest for the maximum pitch value. Since draft is primarily desired from the propeller action, the effective positive pitch angle for a propeller should usually be somewhat less than forty five degrees, there being a practical maximum for a given set of conditions, said maximum being usually desired while a vehicle propelled by a propeller is travelling at a uniform speed. In View of the foregoing, it is usually desirable that the racks be relieved of the aforesaid tensional strain while the blades are set for maximum pitch by a suitable stop means for limiting the rotative displacement of the blades from their zero pitch position. u cordingly, and as shown, stop members 61 are provided, said stops comprising rods threade'dly engaged in threaded perforations 62 provided in the hub bodv whereby the stops extend from the sides 31 of the cavities 16 toward and into the path of movement of the different faces 28 on each member 21. the structure and relation being particularly brought out in Figure 4. For changing the maximumpitch angle, the stop rods 61 are appropriately rotated to dispose their inner ends at the required distances from the cavity sides 31, and for securing the stops in set position; lock plugs 63 are engaged in the perforations 62 and screwed against the rod ends. In this manner, the racks are relieved of strain for most of the time, and a fully operative safety stop is provided should the racks or other operating apparatus fail while under stress, since the stops 61 are seen to operate directly against the members 21, and so, in an operative sense at least, directly against the blades. The stops 61 are also seen to be usable for holding the members 21 during a mounting or dismounting of a propeller blade in the hub.

Preferably. and as shown, a nose-cap 64 is provided at the front end of the hub, said cap eing secured to the hub by means of screws 65 having their heads countersunk in the cap.- It is noted that the cap 64 is in no way associated with the assembly of the propeller and that its removal exposes the forward stops 61 which limit the pulling pitch of the propeller for adjustment, it being clear that adjustment of the rearward reverse stops 61 would be generally unnecessary. Removal of the cap 64 is also seen to expose the head of the pins 23 for permitting their removal when required.

From the foregoing description taken in connection with the accompanying drawings, the advantages of the construction and method of operation will be readily understood by those skilled in the art to which the invention appertains, and while I have described the principle of operation, together with the device which I now consider to be the best embodiment thereof, I desire to have it understood that the device shown is merely illustrative, and that such changes may be made, when desired, as fall within the scope of the appended claims.

Having thus described my invention, I claim as new and desire to secure by Letters Patent of the United States the following:

1. In a propeller, a hub for mounting on a drive shaft, a blade having its shank journalled in said hub to extend radially therefrom, a pinion fixed on said shank and c0- axial therewith, a" sleeve member mounted on the drive shaft for rotation therewith and for axial movement therealong, a rack extending axially from said sleeve member in operative engagement with said pinion whereby an axial displacement of said rack will change the pitch of said blade, and stop means independent of said rack and operable to limit the blade pitch to a desired operative maximum, and means for varying the value of said maximum pitch.

2. In a propeller, a hub providing an axial cavity, a blade having its shank journalled in said hub and extending radially into said cavity, a member fixed on said shank and within said cavity, means for rotatably adjusting said shank about its axis, stop members in the hub cavity independent of said first means and tangentially engageable with said first member for limiting the rotative adjustment of the member and blade between limiting positions thereof, and means for inlependently adjusting the operative positions of said stop members with respect to said first member.

3. In a propeller for aircraft, a hub providing an axial cavity, a blade having its shank journalled in said hub and extending radially into said cavity,-a member fixed on said shank and within said cavity, means for otatably adjusting said shank about its axis, and a stop pin threadedly engaging said hub and extending into said cavity for direct engagement Wit-h said member to limit the rotative adjustment of the member and blade.

4. In a propeller for aircraft, a hub providing an'axial cavity, a blade having its shank .journalled in said hub for rotative said blade.

In testimony whereof, I ailix my signature.

JOSEPH ,P. ROSSI. 

